Process for the production of dimensionally stable, planar materials coated on one side

ABSTRACT

A method of producing dimensionally stable, coated cellulose containing base materials wherein one side of the material is coated in a conventional manner with the customary inorganic or organic coating agents, such as sodium silicate or synthetic resins optionally containing coloring agents, pigments and/or hard powdered materials, such as emery, quartz sand, pulverized glass, silicon carbide, pumice, aluminum oxides, kieselguhr or films, and the other side of the material is impregnated with a solution of a silicone fluid in one or more organic solvents and the solvents are optionally evaporated.

United States Patent Schwarz l l Aug. 19, 1975 PROCESS FOR THEPRODUCTION OF [56] References Cited DIMENSIONALLY STABLE, PLANAR UNITEDSTATES PATENTS MATERIALS COATED ON ONE SIDE 2,768,906 10/1956 James117/68 [75] Inventor: Giinther Schwarz, l-liltrup, Germany 3,163968H1965 51/394 3,432,333 3/1969 Hurst 117/68 [73] Assignee: Glasurit WerkeM. Winkelmann GmbH Primary Examiner-Michael R. Lusignan [22] Filed: May13 1974 Attorney, Agent, or Firm-Gilbert L. Wells [211 Appl. No.:469,292 [57] ABSTRACT Related U 5 Application D A method of producingdimensionally stable, coated [63] Continuation of sen N0 264 588 June 201972 cellulose containing base materials wherein one side aband0ne i ofthe material is coated in a conventional manner with the customaryinorganic or organic coating [30] Foreign Application Priority Dataagents, such as sodium silicate or synthetic resins op- Jul 2 1971German 2132925 tionally containing coloring agents, pigments and/or y yhard powdered materials, such as emery, quartz sand, lverized lasssilicon carbide umice aluminum ..1. -1 [52] U S C 427/21 gg i i g g5 5oxides, kieselguhr or films, and the other side of the [51] Int Cl 2Bose: 9/04 B44D H02 material is impregnated with a solution of asilicone [58] i 68 5 5 R 155 L fluid in one or more organic solvents andthe solvents ll7/l6l L, 161 LN, 161 ZA; 51/394, 399

are optionally evaporated.

5 Claims, N0 Drawings PROCESS FOR THE PRODUCTION OF DIMENSIONALLYSTABLE, PLANAR MATERIALS COATED ON ONE SIDE CROSS REFERENCES TO RELATEDAPPLICATIONS The present application is a Continuation of applicationSer. No. 264,588, filed June 20, 1972, and now abandoned. Applicantclaims priority under 35 U.S.C. 119 for Application P 21 32 925.9, filedJuly 2, 1971 in the Patent Office of the Federal Republic of Germany. Acopy of the priority document is in the file of application Ser. No.264,588.

BACKGROUND OF THE INVENTION 1 This invention relates to a process forthe production of dimensionally stable planar materials of acellulosecontaining substance, which are coated on one side and whichtend to warp, buckle, or bulge due to characteristic physical propertiesof the cellulose-containing substance and the coating applied to oneside.

Cellulose-containing materials, insofar as they are coated on one side,are not dimensionally stable, i.e., these materials warp torsionally orare distorted tensionally, planar materials bulge or are bent to agreater "or lesser extent depending on the thickness of the sheet. Thus,for example, paper webs, cardboards,

hardboard sheets of wood pulp or some other cellulosecontainingmaterial, or vulcanized fiberboard sheets which are unilaterally coatedhave the disadvantageous property of warping to differently strongdegrees, depending on the amount of atmospheric humidity. Thistroublesome, undesirable phenomenon makes it difficult in most cases touse, manipulate, and completely exploit, for example, abrasive belts,emery paper, or abrasive papers, as well as self-adhesive films orselfadhesive wallpapers. Hardboards made from wood pulp or cellulosecompounds are used in furniture manufacture, for house trailers, and forthe interior outfitting of automobile bodies. They furthermore serve asbuilding components in prefabricated house construction. With the use ofhardboards coated on one side, the distortion behavior can cause warpingby tensional forces, and for example, can render furniture or housetrailers manufactured therefrom unattractive after a short period oftime. Also, fastening operations as employed in building construction,for example gluing, affixing, or nailing, can be carried out when thehardboard sheets coated on one side are deformed, only at increasedexpense and by special procedures, without being able to ensuredurability. The only possible countermeasure against warping hasheretofore been to coat these sheets or papers symmetrically on bothsides in the same manner. However,'this can almost never be accomplishedin practice.

SUMMARY OF THE INVENTION It is an object of the present invention toavoid these disadvantageous properties of the coated materials made ofcellulose-containing substances so that they no longer occur, and thematerials remain dimensionally stable.

This problem has been solved, surprisingly, by a process for theproduction of dimensionally stable, coated, planar materials ofcellulose-containing substances which is characterized in that one sideof the material is conventionally coated with the customary inorganic ororganic coating agents, such as, for example, sodium silicate orsynthetic resins which can contain coloring substances, pigments and/orhard powdered materials of various degrees of fineness, such as emery,quartz sand, pulverized glass, silicon carbide, pumice, aluminum oxides,kieselguhr, or film coated, whereas the other side of the material istreated with a solution of a silicone fluid in one or more organicsolvents so that the silicone fluid penetrates into the pores of thematerial and the solvent is optionally evaporated.

Solvents which are hydrophilic are preferred. They are used bythemselves or in a mixture with other organic solvents.

The process is carried out so that 1-30 g./m of a 0.1- percent byweight, preferably 3-10 percent by weight, silicone solution is applied.

The application of the silicone solution takes place directly prior toor after the application of the principal coating on the other side andthe curing thereof, prior to or after the rewetting of the material.

By the terms dimensionally stable according to the present inventionmeans that the materials of cellulosecontaining substances do not warptorsionally or become distorted by tensile effects; that they do notbulge, bend, or become distorted by bending effects, or are deformed inany other manner, as soon as they carry a coating on one side.

The after-treatment of the uncoated side of the materials according tothe present invention, which is simple to execute, surprisingly yieldeda complete, lasting elimination of the deformational phenomena normallypresent. Actually, an increase in warping or bulging was, on thecontrary, to be expected, since silicone fluids, being lubricating andsmoothing substances, can affect the internal, characteristic propertiesof the porous, cellulose-containing material along the lines of aplasticizer, and thus increase the difference in the physical behaviorof the coating with respect to the material substrate, which differenceis responsible for warping.

Materials coated on one side, such as abrasive belts, emery papers, andabrasive paper, as well as hardboard sheets, retained their shape whentreated according to the process of the present invention and could beused and processed substantially more readily and troublefree. Alsostorage tests under various conditions and over rather long periods oftime showed the coated materials to be permanently dimensionally stable,without any warping and changes otherwise occurring in untreatedmaterials coated on one side. It has furthermore been found that, forexample, the surface becomes essentially smoother and more supple.

This unexpectedly advantageous effect is attained by the application ofsilicone fluids in the form of a solution thereof in organic solvents tothe uncated side of the materials of cellulose-containing substances.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Suitable silicone fluids aremethyl siloxanes, methylpolysiloxanes, methylphenyl-siloxanes, andmethylphenylpolysiloxanes, wherein organosubstituents of the same typeor of different types are present, such as, for example, products withethyl and methyl hydrogen groups, as well as such organofunctionalgroups as, for example, B-cyanoethyl, 'y-cyanopropyl, y-trifluoropropyl,S-aminobutyl, and tetrachlorophenyl groups.

Silicone fluids are obtained according to conventional methods by thehydrolysis of chlorosilanes and subsequent condensation and/orpolymerization to cyclic or linear polysiloxanes. Silicone fluids areclear, colorless, neutral, and almost odorless fluids exhibitingviscosities of between 0.65 and 1,000,000 centistokes and a molecularweight of between 600 and 400,000. In technical literature, thesecompounds have been described in detail. Thus, reference is had to thebook Einfuehrung in die Chemie der Silikone [Introduction to SiliconeChemistryl] by Eugene G. Rochow, publishers Chemie G.m.b.l-l.,Weinheim/Bergstrasse, 1952; and U11- manns Encyklopaedie der technischenChemie [Ullmanns Encyclopedia of Technical Chemistry], vol. 15, 1964,pp. 778-782.

Silicone fluids are also disclosed in the Kirk-Othmer Encyclopedia ofChemical Technology, 2nd Edition, Vol. 18, 1969) pages 237-241. Thepreparation of dimethyl silicone fluids is disclosed at page 237, methylphenyl silicone fluids are disclosed at p. 241 along with chlorinatedphenyl groups attached to silicone, methyl trifluoropropyl siliconefluid and methyl alkyl silicone fluids and Table 7 on page 238 disclosesthe properties of Silicone Fluids. US. Pat. Nos. 3,179,619 and 3,050,492cited in Kirk-Othmer disclose homopolymers and copolymers with dimethylsilicone.

The disclosures of these literature and patent references to siliconefluids are incorporated herein.

The silicone fluids are soluble in many organic solvents, such asaliphatic hydrocarbons, aromatic hydrocarbons, esters, furthermoredimethyl sulfoxide, and dimethylformamide. Preferably suitable arehydrophilic solvents, such as alcohols, especially ethyl, propyl, butyl,isopropyl, isobutyl alcohol, furthermore glycols, glycol esters, glycolethers, and glycerin. Examples in this connection are methyl, ethyl,butyl, isobutyl, propyl, and amyl glycol; methyl glycol esters, ethylglycol esters, butyl glycol esters, methyl glycol acetate, ethyl glycolacetate, ethylene glycol, propylene glycol, butyl diglycol, and otherpolyglycols. The solvents can be used individually or in mixtures withone another.

The application of the silicone fluid solution to the uncoated side ofthe materials is effected by means of the usual methods, such as, forexample, brushing, casting, spraying, or rolling. It is particularlyadvantageous to use those silicone fluid solutions which containbetweenabout 0.1 and 50 percent by weight, preferably, however, betweenabout 3 and 10 percent by weight of silicone fluid and 90-97 percent byweight solvent.

The process of this invention is applicable to all materials made ofcellulose-containing substances which are coated on one side. Materialsmade from cellulosecontaining substances are intended to mean allmaterials which contain cellulose-containing matter on the outer surfaceof the material. The materials can have any desired shape, but arepreferably planar materials, such as, for example, sheets, panels, filmswhich can be linear or curved. Among the suitable materials arecardboard, papers, films of cellulose material, hardboards, compositesheets, plywood panels, and vulcanized fiber.

The materials are coated on one side; in other words, they are coveredwith a hardened layer which provides an airtight seal against thesurrounding atmosphere for the material of cellulose-containing matter.Thereby, the cellulose-containing substance can breathe, and themoisture exchange at varying atmospheric humidities can take place, onlytoward the uncoated side.

The materials of cellulose-containing matter can be coated on one sidewith any desired layer which ensures an airtight seal for this side fromthe surrounding atmosphere. These layers can be of an inorganic ororganic character. Thus, suitable substances are, for example, syntheticresins, such as urea-formaldehyde resins, melamine-formaldehyde resins,or phenolformaldehyde resins, alkyd resins, polyester resins, polyamideresins, epoxy compounds, polyurethanes, polysulfides, polybutadiene,chlorinated rubber, polyethylene, polypropylene, and many others.

It is furthermore possible to embed into the synthetic resins coloringagents, hard powders of various degrees of fineness, and pigments,such'as, for example, emery, quartz sand, powdered glass, carbides,silicon carbide, pumice, aluminum oxides, kieselguhr, polishing agents,etc.

The coating can furthermore consist of an inorganic material, e.g.sodium silicate.

The production of such coatings does not pertain to the subject matterof the present application. They can be applied in a conventional mannerby rolling, spraying, calendering the coating agents from solutions inorganic solvents or from aqueous dispersions. It is also possible topress films against the substrate. Thereafter, the coating can be driedand cured in the usual manner. The curing process is omitted in themanufacture of self-adhesive films. After the coated side has been curedby baking at elevated temperatures in the usual manner, the material ofcellulose-containing matter contains only minor amounts of moisture. Inorder to restore the equilibrium with respect to the atmospherichumidity, a rewetting is generally carried out after the curingprocedure, by spraying the uncoated side with water.

According to the process of the present invention, the silicone fluidsolution is applied prior to or after the curing process and prior to orafter the rewetting step.

The materials coated on one side and obtained according to the processof the present invention are required for a great variety of fields ofapplication. Thus, it is, above all, possible to'produce abrasive papersand abrasive belts in a dimensionally stable form. Also hardboards andplywood panels can find a broadened application in the furniture, housetrailer, and building industries. Also vulcanized fiberboards remaindimensionally stable. Further fields of use are the treatment ofself-adhesive films, self-adhesive wallpapers, as well as postagestamps.

The following examples are to explain the process of this inventionwithout limiting same. All percentage data relate to percent by weightand all parts are parts by weight.

EXAMPLE 1 An abrasive belt, coated on one side with a phenolic resin andthe usual abrasive agents, is treated on the uncoated side with asolution of 5 parts by weight of phenyl methyl siloxane (having thetrade name silicone oil EXAMPLE 2 A hardboard panel, covered on one sidewith a varnish coat of an acid-curing varnish with a layer thickness of50-100 micron, is treated on the backside by rolling thereonto asolution of 6 parts of a methylpolysiloxane (having the tradenamesilicone oil M from Bayer AG, Leverkusen, Germany) in a mixture of butylglycol and glycerin (80:20). In this way, -17 g./m is applied. Ahardboard panel is thus obtained which retains its smooth form and doesnot warp even at extreme atmospheric humidity values.

EXAMPLE 3 A paper web coated with a phenolic resin wherein emery isembedded and exhibiting a thickness of 1.2 mm. is sprayed on theuncoated side with a solution of 5 parts by weight of silicone oil M (asdescribed in example 2) in a mixture of 60 parts of toluene,,l5 parts ofmonoglycol butyl ether, and 15 parts of isobutanol, so that about 15-17g./m is thus applied.'Aft er drying for 10 hours at 60C in a dryingchamber, the dimensional stability was retained without change after astorage period of 6 weeks at a relative atmospheric humidity of 80percent, whereas an identical sample treated only with the solventmixture without the silicone fluid in the same manner exhibited strongwarpage after a short storage period of hours.

EXAMPLE 4 A solution of 5 parts by weight of silicone oil PL (asdescribed in example 1) in a mixture of 90 percent of mineral spirit and10 percent of butanol is rolled onto the backside of a hardboard panelprovided with an epoxy coating, immediately after baking the epoxycoating. After drying in air, the uncoated backside is sprayed withwater. About 14 g./m of the silicone fluid solution is applied. Thethus-treated hardboard panel retains it smooth, dimensionally stableshape and shows no tendency toward bulging.

EXAMPLE Papers coated on one side, e.g. postage stamps or wallpaperswherein the coating consists of a glue film are treated, on the uncoatedside a. prior to the glue application,

b. simultaneously with the glue application, or

c. after the glue application with an 8 percent solution of amethylpolysiloxane (having the tradename silicone oil M from Bayer AG,Leverkusen, Germany) in butyl diglycol by spreading.

The amount of silicone oil solution applied depends on the weight of thepaper and on the compression of the paper and amounts, on the average,to between 5 and 30 g./m After drying, gummed papers (postage stamps orwallpapers) are obtained which neither bulge nor warp.

EXAMPLE 6 A self-adhesive surfacing or decorative sheet wherein thesubstrate consists of papers impregnated with ureaformaldehyde ormelamine-formaldehyde or phenolformaldehyde resins and the self-adhesivecoating consits of melamine resin or urea resin, is treated with thesilicone fluid solution as indicated in Example 1. After drying, theself-adhesive foils do not warp and retain their smooth shape on apermanent basis.

EXAMPLE 7 For comparison purposes, an abrasive belt coated, as describedin Example 1, on one side with a phenolic resin and the usual abrasiveagents, is treated on the uncoated side by rolling with a mixture ofbutyl glycol and glycerin (:20). As in Example 1, 10-15 g./m is appliedby rolling. The abrasive belt obtained after evaporation of the solventretains its smooth shape only temporarily and is warped again after ashort period of time.

1 claim:

1. A method for producing a dimensionally stable porous cellulosicsubstrate by impregnating the uncoated side opposite to that bearing amoistureproof impermeable surface coating with silicone fluids, anddrying said coating, the improvement comprising applying to saiduncoated side of said substrate a solution containing 97 percent byweight of a solvent selected from the group consisting of organichydrophilic solvents or solvents containing not less than 10 percent ofsaid hydrophilic solvents and 3 10 percent by weight silicone fluidhaving a viscosity of 0.65 1,000,000 centistokes and a molecular weightbetween about 600 400,000.

2 The method of claim 1, wherein said impermeable surface coating isselected from the group consisting of sodium silicate and syntheticresins.

3. The method of claim 1, wherein said impermeable surface coating is apressed film.

4. The method of claim 1, wherein said base sheet material is exposed tomoisture prior to the application of said silicone fluid.

5. The product obtained by the method of claim 1.

1. A METHOD FOR PRODUCING A DIMENSIONALLY STABLE POROUS CELULOSICSUBSTRATE BY IMPREDGNATING THE UNCOATED SIDE OPPOSITE TO THAT BEARING AMOISTUREPROOF IMPEREABLE SURFACE COATING WITH SILICONE FLUIDS, ANDDRYING SAID COATING, THE IMPROVEMENT COMPRISING APPLYING TO SAIDUNCOATED SIDE OF SAID SUBSTRAYE A SOLUTION CONTAINING 90 - 97 PERCENT BYWEIGHT OF A SOLVENTS SELECTED FROM THE GROUP CONSISTING OF ORGANICHYDROPHILLIC SOLVENTS OR SOLVENTS CONTAINING NOT LESS THAN 10 PERCENT OFSAID HYDROPHILIC SOLVENTS AND 3 - 10 PERCENT BY WEIGHT SILICONE FLUIDHAVING A VISCOSITY OF 0.65 - 1,000,000 CENTISTOKES AND A MOLECULARWEIGHT BETWEEN ABOUT 600 - 400,000.
 2. The method of claim 1, whereinsaid impermeable surface coating is selected from the group consistingof sodium silicate and synthetic resins.
 3. The method of claim 1,wherein said impermeable surface coating is a pressed film.
 4. Themethod of claim 1, wherein said base sheet material is exposed tomoisture prior to the application of said silicone fluid.
 5. The productobtained by the method of claim 1.